The invention relates to a safety system in accordance with the preamble of claim 1.
Safety systems of this type are generally used for safety-related applications, in particular for safeguarding danger zones on machines. These danger zones can, in particular, be provided with fences in which a door is arranged as a protective device. The door is secured in a closed position via the safety system to prevent unauthorized access to the danger zone.
The safety system prevents dangerous machine functions from being carried out with the actuation system of the machine as long as the separating protective device, meaning the door, is open.
A safety system of that type is the MGB system of the company Euchner GmbH+Co. KG, as an example. This safety system is comprised of a bolting mechanism via which a separating protective device like a door can be securely bolted in place. The MGB has a handle module arranged on the door in connection with this and a bolting module fixed in place on a frame or the like. A bolt tongue on the handle module is inserted into a receptacle in the bolting module to bolt the door. The bolting of the door can be registered in that a bolting module is detected in the transponder, as a first monitoring device that is arranged on the bolt tongue, via a reading unit when the bolt tongue is inserted into the receptacle.
To increase the functional reliability of the safety system, it has a second monitoring device that is likewise designed in the form of a transponder via which the door position is detected.
In general, further signals are generated with the second monitoring device; the overall system is also secured above and beyond the required range because of that. In particular, this additional safeguard serves to reveal error cases of the first monitoring device. If a defect exists in the first monitoring device, for instance, to the effect that the first monitoring device signals, despite an unbolted door, a bolted state, although this does not exist, the door position can be registered with the second monitoring device and the situation can be detected, in particular, when the door is open. In this case, the malfunction of the first monitoring device is revealed by the second monitoring device and the safety system can bring about a safe condition by initiating an emergency stop for the machine.
The drawback with this system is that the first and second monitoring devices are comprised of a transponder; the transponders are arranged at such a short distance from one another that they could reciprocally influence one another, which can lead to malfunctions of the safety system.